dvb_si/descriptors/
time_shifted_event.rs

1//! Time Shifted Event Descriptor — ETSI EN 300 468 §6.2.44 (tag 0x4F).
2//!
3//! Table 103 (PDF p. 109). Carried in the EIT for an NVOD time-shifted
4//! event; points at the reference service + event it shifts. Body is a 16-bit
5//! `reference_service_id` followed by a 16-bit `reference_event_id`.
6
7use super::descriptor_body;
8use crate::error::{Error, Result};
9use dvb_common::{Parse, Serialize};
10
11/// Descriptor tag for time_shifted_event_descriptor.
12pub const TAG: u8 = 0x4F;
13const HEADER_LEN: usize = 2;
14const BODY_LEN: usize = 4;
15
16/// Time Shifted Event Descriptor.
17#[derive(Debug, Clone, Copy, PartialEq, Eq)]
18#[cfg_attr(feature = "serde", derive(serde::Serialize))]
19pub struct TimeShiftedEventDescriptor {
20    /// service_id of the reference (NVOD reference) service.
21    pub reference_service_id: u16,
22    /// event_id of the reference event within that service.
23    pub reference_event_id: u16,
24}
25
26impl<'a> Parse<'a> for TimeShiftedEventDescriptor {
27    type Error = crate::error::Error;
28    fn parse(bytes: &'a [u8]) -> Result<Self> {
29        let body = descriptor_body(
30            bytes,
31            TAG,
32            "TimeShiftedEventDescriptor",
33            "unexpected tag for time_shifted_event_descriptor",
34        )?;
35        if body.len() != BODY_LEN {
36            return Err(Error::InvalidDescriptor {
37                tag: TAG,
38                reason: "time_shifted_event_descriptor length must be 4",
39            });
40        }
41        let (hdr, _) = body
42            .split_first_chunk::<4>()
43            .ok_or(Error::InvalidDescriptor {
44                tag: TAG,
45                reason: "time_shifted_event_descriptor length must be 4",
46            })?;
47        Ok(Self {
48            reference_service_id: u16::from_be_bytes([hdr[0], hdr[1]]),
49            reference_event_id: u16::from_be_bytes([hdr[2], hdr[3]]),
50        })
51    }
52}
53
54impl Serialize for TimeShiftedEventDescriptor {
55    type Error = crate::error::Error;
56    fn serialized_len(&self) -> usize {
57        HEADER_LEN + BODY_LEN
58    }
59
60    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
61        let len = self.serialized_len();
62        if buf.len() < len {
63            return Err(Error::OutputBufferTooSmall {
64                need: len,
65                have: buf.len(),
66            });
67        }
68        buf[0] = TAG;
69        buf[1] = BODY_LEN as u8;
70        buf[2..4].copy_from_slice(&self.reference_service_id.to_be_bytes());
71        buf[4..6].copy_from_slice(&self.reference_event_id.to_be_bytes());
72        Ok(len)
73    }
74}
75impl<'a> crate::traits::DescriptorDef<'a> for TimeShiftedEventDescriptor {
76    const TAG: u8 = TAG;
77    const NAME: &'static str = "TIME_SHIFTED_EVENT";
78}
79
80#[cfg(test)]
81mod tests {
82    use super::*;
83
84    #[test]
85    fn parse_reference_ids() {
86        let bytes = [TAG, 4, 0x12, 0x34, 0x56, 0x78];
87        let d = TimeShiftedEventDescriptor::parse(&bytes).unwrap();
88        assert_eq!(d.reference_service_id, 0x1234);
89        assert_eq!(d.reference_event_id, 0x5678);
90    }
91
92    #[test]
93    fn parse_rejects_wrong_tag() {
94        assert!(matches!(
95            TimeShiftedEventDescriptor::parse(&[0x50, 4, 0, 0, 0, 0]).unwrap_err(),
96            Error::InvalidDescriptor { tag: 0x50, .. }
97        ));
98    }
99
100    #[test]
101    fn parse_rejects_short_buffer() {
102        // declares length 4 but only 3 body bytes present
103        let bytes = [TAG, 4, 0x12, 0x34, 0x56];
104        assert!(matches!(
105            TimeShiftedEventDescriptor::parse(&bytes).unwrap_err(),
106            Error::BufferTooShort { .. }
107        ));
108    }
109
110    #[test]
111    fn parse_rejects_wrong_length() {
112        let bytes = [TAG, 5, 0x12, 0x34, 0x56, 0x78, 0x00];
113        assert!(matches!(
114            TimeShiftedEventDescriptor::parse(&bytes).unwrap_err(),
115            Error::InvalidDescriptor { tag: TAG, .. }
116        ));
117    }
118
119    #[test]
120    fn serialize_round_trip() {
121        let d = TimeShiftedEventDescriptor {
122            reference_service_id: 0xABCD,
123            reference_event_id: 0x0102,
124        };
125        let mut buf = vec![0u8; d.serialized_len()];
126        d.serialize_into(&mut buf).unwrap();
127        assert_eq!(TimeShiftedEventDescriptor::parse(&buf).unwrap(), d);
128    }
129
130    #[test]
131    fn serialize_rejects_small_buffer() {
132        let d = TimeShiftedEventDescriptor {
133            reference_service_id: 1,
134            reference_event_id: 2,
135        };
136        let mut tiny = [0u8; 5];
137        assert!(matches!(
138            d.serialize_into(&mut tiny).unwrap_err(),
139            Error::OutputBufferTooSmall { .. }
140        ));
141    }
142
143    #[cfg(feature = "serde")]
144    #[test]
145    fn serde_round_trip() {
146        let d = TimeShiftedEventDescriptor {
147            reference_service_id: 0x1234,
148            reference_event_id: 0x5678,
149        };
150        let json = serde_json::to_string(&d).unwrap();
151        // Serialize-only: assert the emitted JSON re-parses (serialize-stable).
152        let _v: serde_json::Value = serde_json::from_str(&json).unwrap();
153    }
154}
dvb_si/descriptors/time_shifted_event.rs

dvb_si/descriptors/
time_shifted_event.rs
